Patent GB-873517-A (GB)
Title: Improvements in hydraulic starting and pumping devices for internal combustion engines
IPC: F16H39/00
Filed: 1960-01-19
Abstract: 873,517. Liquid pressure engines. NEW YORK AIR BRAKE CO. Jan. 19 1960 [Jan. 29, 1959], No. 1874/60. Class 69 (2). Also in Groups XXVII and XXVIII] An hydraulic engine and pump for an engine starting and pumping device (see Group XXVII) is described. As shown in Fig. 1, the hydraulic engine comprises a housing having separable sections 21 and 22 which are connected together by bolts 23 and which, when assembled, locate and rigidly hold an intermediate wall 24. A valve plate 25, containing arcuate high and low pressure ports 26 and 27 (see Figs. 3 and 4) which communicate with the high and low pressure ports 28 and 29 of the hydraulic engine, is freely seated within a bore formed in housing section 22 and is prevented from rotating by pin 31. A drive shaft 32 is journalled in intermediate wall 24 and in valve plate 25 for supporting and driving rotary cylinder barrel 33. The cylinder barrel is formed with an axial bore 34 which is in great circle engagement with spherical enlargement 35 carried by shaft 32 for providing a universal and axially slidable support for the cylinder barrel. A torque tube 36, connected by splines 37 and 38 at its opposite ends with the cylinder barrel 33 and with the drive shaft 32, joins these members in driving relationship. The cylinder barrel 33 contains a circumferential series of through longitudinal cylinder bores 39 which are arranged to register sequentially with the arcuate ports 26 and 27 as the cylinder barrel rotates. A spring 41, reacting between split ring 42 carried by the torque tube and collar 43 carried by the cylinder barrel, biases the cylinder barrel 33 into engagement with the valve plate 25. The spring load imposed on the torque tube is transmitted to the shaft by splines 38 and ring 44. Pistons 45, formed with spherical heads 46 for supporting shoes 47, are mounted in cylinder bores 39 for reciprocation by cam plate 48 and nutating plate 49. Nutating plate 49 is seated on a collar 51 having a spherical outer surface which engages a similarly shaped recess formed in the nutating plate. The centre of this spherical surface, as well as the centre of spherical enlargement 35, is located at the point of intersection 52 of the axis of the drive shaft and the plane of the centres of spherical piston heads 46. Snap ring 53, seated in a groove formed in drive shaft 32, prevents longitudinal movement of collar 51 under the action of the piston inertia loads and thus serves to transmit these loads into shaft 32. The loads are conveyed from the shaft to the housing section 22 by thrust bearing 54. Cam plate 48 is supported in housing section 22 by yokes 55, 55<SP>1</SP> and trunnions 56, 56<SP>1</SP> for angular movement about an axis extending in a direction normal to the axis of drive shaft 32 and intersecting that axis at the point 52. The angular position of the cam plate determines the length of the strokes of pistons 45 and the cam plate is free to move between maximum stroke establishing positions on opposite sides of a neutral or zero stroke establishing position (a vertical position as viewed in Fig. 1). A spring plunger 57, connected with the lower end of the cam plate 48 by an articulated connecting rod 58, biases the cam plate toward its maximum stroke establishing position on the right or motoring side of neutral. The cam plate 48 is moved to the opposite or pumping side of neutral against the bias of spring plunger 57 by a shifting motor 59. This motor comprises a cylinder 61, a reciprocable piston 62, and a closed motor working chamber 63. The piston 62 is connected with the cam plate by articulated connecting rod 64. Surrounding the cylinder 61 is a coaxial cylinder 65 which defines an annular space for receiving the shiftable spring seat 66. This seat slides along and is in sealing engagement with the surfaces of the cylinders 61 and 65. A cap 67, threaded on the left end of cylinder 65, serves as a stop which limits the leftward movement of spring seat 66. The space 68 to the right of the spring seat 66 is connected with the working chamber of the shifting motor 59 by a passage 69. A biasing spring 71, reacting between the seat 66 and the piston 62, urges the cam plate 48 towards its maximum stroke establishing position on the pumping side of neutral. A control motor 72 comprising a cylinder 73, a working chamber 74, and a reciprocable piston 75 connected with the cam plate 48 by articulated connecting rod 76, serves to shift the cam plate toward its neutral position against the bias of spring 71 and shifting motor 59. Journalled in housing sections 21 and 22 is a power shaft 77 which is connected with the internal combustion engine (not shown) by a splined coupling 78. Encircling power shaft 77 are two spur gears 79 and 81 whose hubs 82 and 83 are journalled in intermediate housing wall 24. The hub portion 80 of gear 81 is journalled in housing section 22 and supports the right end of power shaft 77. These gears are connected with the power shaft by one-way overrunning clutches 84 and 85 and are arranged to engage spur gears 86 and 87 which are formed as an integral part of drive shaft 32. The cam elements 88 of clutches 84 and 85 are set in reverse senses so that when the shaft 32 is driving the shaft 77, torque is transmitted through gears 86 and 79, and when power shaft 77 is driving drive shaft 32, torque is transmitted through gears 81 and 87. Both gear pairs 79, 86 and 81, 87 effect a step-down in speed; the pair 79, 86 having the higher ratio. The pressure in working chamber 74, acting on control piston 75, urges the cam plate 48 toward its neutral position against the bias of spring 71 and shifting motor piston 62. The parts are so dimensioned that when the discharge pressure in passage 95 reaches either of the two maximums, the cam plate 48 will be in its neutral position. The following numerical example will illustrate this point: Let it be assumed that (1) the lower maximum discharge pressure is 3000 p.s.i. and the higher maximum discharge pressure is 4000 p.s.i.; (2) the control pressure differential of cam plate 48, i.e., the difference in pressure in working chamber 74 which will cause cam plate 48 to move between its maximum and neutral positions, is 30 p.s.i.; (3) the effective area of piston 75 of control motor 72 is 1 square inch; (4) the effective area of piston 62 of shifting motor 59 is 0.495 square inches; (5) spring 71 exerts no force on cam plate 48 when the cam plate is in its maximum stroke establishing positions; and (6) spring 71 exerts a force of 15 pounds when cam plate 48 is in its neutral position. Using these values and considering first the operation when solenoid 158 is de-energized and space 149 is vented, it will be seen that a pressure of 1500 p.s.i. will be required in working chamber 74 of control motor 72 in order to hold cam plate 48 in its neutral position when discharge pressure is 3000 p.s.i. Since the pressure in this working chamber equals the difference between discharge pressure and the " reference pressure," the " reference pressure " in this case must be 1500 p.s.i. This means that spring 146 will vent working chamber 74 until discharge pressure reaches 1500 p.s.i. and that when the discharge pressure exceeds this value, the pressure in that working chamber will increase at the same rate as the discharge pressure. When the discharge pressure reaches 2970 p.s.i., the pressure in working chamber 74 will have increased to 1470 p.s.i. and at this point the force developed by control motor 72 will just balance the sum of the forces developed by spring 71 and shifting motor 59. The next 30 p.s.i. increase in discharge pressure will cause control motor 72 to move the cam plate from its maximum to its neutral stroke establishing position. If discharge pressure should now decrease, valve plunger 134 will be shifted to the left from its lap position by spring 146 and the fluid pressure in spring chamber 143, thereby interconnecting ports 129 and 131 and venting working chamber 74. When the pressure in this chamber again equals the difference between discharge pressure and the " reference pressure," valve plunger 134 will again move to the right to its lap position. If discharge pressure should drop below the " reference pressure " of 1500 p.s.i., valve plunger 134 will take up a position to the left of its lap position. When solenoid 158 is energized and the space 149 to the right of shiftable spring seat 142 is pressurized, this seat will move to the left and compress spring 146. The area of spring seat 142, which is subject to the pressure in space 149, is so selected that the preload induced in spring 146 will establish a " reference pressure " of 2005 p.s.i. Operation of the discharge pressure compensator under high pressure conditions is basically the same as it is under low pressure conditions. When discharge pressure is below the " reference pressure " of 2005 p.s.i., working chamber 74 is vented and when discharge pressure rises above this value, the pressure established in working chamber 74 equals the difference between discharge pressure and the " reference pressure." At a discharge pressure of 3970 p.s.i., the pressure in working chamber 74 will be 1965 p.s.i. and the force developed by control motor 72 will just balance the forces exerted by shifting motor 59 and spring 71. As the discharge pressure rises to 4000 p.s.i., the pressure in working chamber 74 will increase progressively to 1995 p.s.i. and the cam plate 48 will be moved gradually toward its neutral position. When discharge pressure reaches 4000 p.s.i., the force developed by control motor 72 will just balance the sum of the forces developed by spring 71 and shifting motor 59 and the cam plate 48 will be in its neutral position. It should be observed that when the discharge pressure compensator establishes a maximum desirable pressure of 4000 p.s.i., spring seat 142 is subjected to two variable pressures, namely, the pr